2019年下半年英语四级阅读练习：电的影响
Can electricity cause cancer? In a society that literally runs on electric power, the very idea seems preposterous. But for more than a decade, a growing band of scientists and journalists has pointed to studies that seem to link exposure to electromagnetic fields with increased risk of leukemia and other malignancies. The implications are unsettling, to say the least, since everyone comes into contact with such fields, which are generated by everything electrical, from power lines and antennas to personal computers and micro-wave ovens. Because evidence on the subject is inconclusive and often contradictory, it has been hard to decide whether concern about the health effects of electricity is legitimate—or the worst kind of paranoia.
Now the alarmists have gained some qualified support from the U.S. Environmental Protection Agency. In the executive summary of a new scientific review, released in draft form late last week, the EPA has put forward what amounts to the most serious government warning to date. The agency tentatively concludes that scientific evidence"suggests a casual link" between extremely low-frequency electromagnetic fields—those having very longwave-lengths—and leukemia, lymphoma and brain cancer, While the report falls short of classifying ELF fields as probable carcinogens, it does identify the common 60-hertz magnetic field as "a possible, but not proven, cause of cancer in humans."
The report is no reason to panic—or even to lost sleep. If there is a cancer risk, it is a small one. The evidence is still so controversial that the draft stirred a great deal of debate within the Bush Administration, and the EPA released it over strong objections from the Pentagon and the White House. But now no one can deny that the issue must be taken seriously and that much more research is needed.
At the heart of the debate is a simple and well-understood physical phenomenon: When an electric current passes through a wire, tit generates an electromagnetic field that exerts forces on surrounding objects, For many years, scientists dismissed any suggestion that such forces might be harmful, primarily because they are so extraordinarily weak. The ELF magnetic field generated by a video terminal measures only a few milligauss, or about one-hundredth the strength of the earth's own magnetic field, The electric fields surrounding a power line can be as high as 10 kilovolts per meter, but the corresponding field induced in human cells will be only about 1 millivolt per meter. This is far less than the electric fields that the cells themselves generate.
How could such minuscule forces pose a health danger? The consensus used to be that they could not, and for decades scientists concentrated on more powerful kinds of radiation, like X-rays, that pack sufficient wallop to knock electrons out of the molecules that make up the human body. Such "ionizing" radiations have been clearly linked to increased cancer risks and there are regulations to control emissions.
But epidemiological studies, which find statistical associations between sets of data, do not prove cause and effect. Though there is a body of laboratory work showing that exposure to ELF fields can have biological effects on animal tissues, a mechanism by which those effects could lead to cancerous growths has never been found.
The Pentagon is for from persuaded. In a blistering 33-page critique of the EPA report, Air Force scientists charge its authors with having "biased the entire document" toward proving a link. "Our reviewers are convinced that there is no suggestion that (electromagnetic fields) present in the environment induce or promote cancer," the Air Force concludes. " It is astonishing that the EPA would lend its imprimatur on this report." Then Pentagon's concern is understandable. There is hardly a unit of the modern military that does not depend on the heavy use of some kind of electronic equipment, from huge ground-based radar towers to the defense systems built into every warship and plane.
英语四级阅读练习练习题：
1. The main idea of this passage is
[A]. studies on the cause of cancer
[B]. controversial view-points in the cause of cancer
[C]. the relationship between electricity and cancer.
[D]. different ideas about the effect of electricity on caner.
2. The view-point of the EPA is
[A]. there is casual link between electricity and cancer.
[B]. electricity really affects cancer.
[C]. controversial.
[D].low frequency electromagnetic field is a possible cause of cancer
3. Why did the Pentagon and Whit House object to the release of the report? Because
[A]. it may stir a great deal of debate among the Bush Administration.
[B]. every unit of the modern military has depended on the heavy use of some kind of electronic equipment.
[C]. the Pentagon's concern was understandable.
[D]. they had different arguments.
4. It can be inferred from physical phenomenon
[A]. the force of the electromagnetic field is too weak to be harmful.
[B]. the force of the electromagnetic field is weaker than the electric field that the cells generate.
[C]. electromagnetic field may affect health.
[D]. only more powerful radiation can knock electron out of human body.
5. What do you think ordinary citizens may do after reading the different arguments?
[A].They are indifferent. [B]. They are worried very much.
[C]. The may exercise prudent avoidance. [C]. They are shocked.
英语四级阅读练习答案详解：
1. D 电力对癌症影响的不同观点。文章一开始就提出了“电会致癌吗?”这个问题。十多年来，一大批科学家和新闻界人士都指出：研究结果似乎表示：接触电磁场可能会增加患白血病和其他恶性肿瘤的危险性。所以说到目前为止还难以确定电力对健康的影响究竟是理性的，还是杞人忧天。见难句注释1。第二段公布了环保署的报告，见难句注释3。第三段说明：即使有致癌危险也是极微的。但应予以认真对待，进行更多的研究。而第七段中空军方面的科学家还没有被说服(见难句注释9)，明确提出，我们的评论员认为没有迹象说明环境中存在的电力会诱发或促发癌症。A. 对致癌因素的研究。 B. 致癌原因方面有争议的观点，这两项根本部队，和文内电力毫无关系。C. 电力和癌症的关系，文中涉及的是电力究竟会不会致癌的两种观点，而不是两者之关系。
2. A. 电和致癌有一定难以确定的关系。答案在第二段第三句，环保署目前的结论是据科学证据指出极低频电磁场——具有长波的电磁场——和白血病，淋巴瘤及脑癌之间有着难以确定的联系，见难句注释3。A. 电确实致癌，不对。 C. 有争议的。说的不够清楚，争议什么。 D. 低频磁场是一个可能致癌因素。这只是论点的一面。
3. B. 现代军事的任何部门都一直依赖于应用大量应用电子设备。五角大楼和白宫所以反对环保署公布报告之理由就在此。空军方面的专家所以说环保署方面的报告“歪曲了整个文件以证明两者之间的关系”也在此。见难句注释4。所以文内说“角大楼的关注是可以理解的。”A. 报告会在布什政府内引起大规模的辩论，这是结果。 C. 五角大楼的关注是可以理解的，这不是原因。 D. 他们有不同的观点。
4. 磁场力太弱不会产生有害作用。答案在第四段第二，三句，当电流通过电缆，产生磁场，对周围物体产生(影响)力。许多年来，科学家把任何有关“这些力可能有害的想法”置于一边(不予考虑)，主要是因为它们(所产生的力)非常弱。B. 磁场力比细胞产生的电磁场弱。只是明确指出的事实。 C. 磁场力对人的健康有害。不对。 D. 只有更强的辐射才能把人体中的电子击出来。不对。
5. C. 他们会采取谨慎小心避开电器的途径。因为他们不可能象A项那样漠不关心。这种问题直接影响人的生命。B. 他们非常担忧。 D. 他们感到震惊，这两项都不可能，因为还在争议中，的途径是尽量避开和电器接触。
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